1. Field of the Invention
The present invention is generally related to a marine propulsion apparatus and, more particularly, to a marine propulsion apparatus that employs an engine with an output shaft extending in a forward direction, the output shaft being coupled, in torque transmitting relation, with a pair of driveshafts that extend in an aft direction and which are attached in torque transmitting relation with individual propellers.
2. Description of the Prior Art
Many different types of marine propulsion systems are known to those skilled in the art. These systems are typically classified as inboard drives, outboard motors, or stern drive systems, but many other arrangement are also known to those skilled in the art. In an article titled xe2x80x9cSmallcraft Propulsionxe2x80x9d by Robert W. Hobbs, which appeared in Popular Boating Magazine in 1962, the author describes twenty-five different arrangements of marine propulsion systems. In some systems, described in the Hobbs article, the engine is arranged with an output shaft extending in an aft direction, towards the transom of a marine vessel. In other applications, the engine is arranged with its output shaft extending in a forward direction, toward the bow of the marine vessel. Some of the systems employ the propeller arranged in a conventional arrangement, in which the propeller provides a thrust that xe2x80x9cpushesxe2x80x9d the marine vessel forward while other arrangements employ a propeller in a xe2x80x9ctractorxe2x80x9d arrangement.
U.S. Pat. No. 3,207,118, which issued to Baldwin on Sep. 21, 1965, describes improvements in boat propulsion systems. It specifically provides a propulsion system where the steering ability is made easier and more effective. The propellers are positioned so that the force of the water backward under the boat has a stabilizing influence on the boat, materially lessening the rolling and pitching of the boat even in high seas.
U.S. Pat. No. 1,883,661, which issued to Fernstrum on Oct. 18, 1932, describes a marine motor which provides for the mounting of both its flywheel and accessory shaft drive at the forward end of the engine. The V-belt drive is accommodated to the usual forward mounting of the flywheel in marine practice. Moreover, particular ease in changing the V-belt is enabled by mounting the belt at the forward face of the flywheel so that a new belt need not be positioned behind a rotating member.
U.S. Pat. No. 6,142,841, which was issued to Alexander et al on Nov. 7, 2000, describes a water jet docking control system for a marine vessel. The maneuvering control system utilizes pressurized liquid at three or more positions of a marine vessel in order to selectively create thrust that moves the vessel into desired locations and according to chosen movements. The outlook conduits are mounted to the hull of the vessel and direct streams of liquid away from the vessel for purposes of creating thrusts which move the vessel as desired. Electrical embodiments of the device can utilize one or more pairs of impellers to cause fluid to flow through outlet conduits in order to provide thrust on the marine vessel.
U.S. Pat. No. 6,234,853, which was issued on May 22, 2000, by Lanyi et al discloses a simplified docking method and apparatus for a multiple engine marine vessel. The docking system utilizes the marine propulsion unit of a marine vessel, under the control of an engine control unit that receives command signals from a joystick or push button device, to respond to a maneuver command from the marine operator. The docking system does not require additional propulsion devices other than those normally used to operate the marine vessel under normal conditions. The docking system uses two marine propulsion units to respond to an operator""s command signal and allows the operator to select forward or reverse commands in combination with clockwise or counterclockwise rotational commands, either in combination with each other or alone.
The patents described above are hereby expressly incorporated by reference in the following description of the present invention.
In the prior art, it is known that a pair of propulsion devices, such as two outboard motors or two stern drive systems, can be used in combination with each other to maneuver a marine vessel in response to commands received from the operator of the vessel. It is also known that bow thrusters, which provide a force on the marine vessel that is perpendicular to the vessel""s centerline which extends from bow to stern, can be used to assist in maneuvering and docking operations. Although various devices are known in the prior art to accomplish the goal of maneuvering a marine vessel, known devices also have certain disadvantages. For example, in marine propulsion systems that utilize an internal combustion engine supported within the hull of the vessel, the use of various types of transmissions between the engine and the propeller shafts requires that the internal combustion engine be spaced apart from the transom by a sufficient distance to allow the transmission or other devices to be located within the marine vessel, in front of the transom and behind the engine. This requires that the engine be moved forward within the hull of the marine vessel and this can lead to certain disadvantage locations of the center of gravity of the vessel and, in addition, can reduce the allowed space available for other purposes within the hull structure of the marine vessel.
A marine propulsion apparatus made in accordance with the present invention comprises an engine that is disposable in a marine vessel. An output shaft of the engine extends from the engine in a forward direction away from a transom of the marine vessel. First and second torque transmitting devices, such as pulleys, are attached in torque transmitting relation with the output shaft of the engine and located forward of the engine. A first driveshaft is connected in torque transmitting relation with the first torque transmitting device and extends in an aft direction from the first torque transmitting device at the front part of the engine. A second driveshaft is connected in torque transmitting relation with the second torque transmitting device at the front of the engine and the second driveshaft extends in an aft direction from the second torque transmitting device.
A particularly preferred embodiment of the present invention further comprises a bow thruster for exerting a thrust vector in a direction that is generally perpendicular to a central axis extending from a bow of the marine vessel to a stern of the marine vessel. The first torque transmitting device can be a first pulley connected in torque transmitting relation with the output shaft and the second torque transmitting device can be a second pulley connected in torque transmitting relation with the output shaft.
The present invention can further comprise a first driveshaft pulley attached to the first driveshaft and a second driveshaft pulley attached to the second driveshaft. The first and second driveshafts can extend through the transom of the marine vessel in one embodiment of the present invention. In alternative embodiments, the first and second driveshafts can extend through the bottom of the marine vessel or, alternatively, through the transom and in torque transmitting relation with two stern drive units.
In one embodiment of the present invention, it further comprises a first stern drive apparatus and a second stern drive apparatus attached to the transom of the marine vessel and a propeller supported for rotation by each of the first and second stern drive apparatus, whereby each propeller is connected in torque transmitting relation with its associated driveshaft. Alternatively, the first and second propellers can be attached directly to the first and second driveshafts.